Field of the Invention
The invention relates to a method and implants to treat a knee with an injured or ruptured anterior cruciate ligament.
Discussion of Related Art
The Anterior Cruciate Ligament (ACL) in the human knee joint, commonly called Cranial Cruciate Ligament (CrCL) in the canine stifle, is frequently torn in trauma. It also frequently fails, particularly in dogs, after, a degenerative process of still unknown etiology.
In human orthopedics, the standard procedure calls for replacement by an ACL allograft, a part of the patient's own patellar ligament, or a part of the tendon removed from his hamstring muscle. The procedure results in a stable knee, but the long-term performance is often unsatisfactory—75 to 90% of cases result in arthrosis of the joint within 15 years of the procedure.
In dogs, the standard procedure is either an extra capsular suture or one of several geometry modifying surgical techniques. In the extra capsular procedure, a suture is placed outside of the joint, usually on the lateral side, to approximate the function of the ligament. The intention of the suture is to provide stability of the joint for several weeks, while waiting for fibrosis to form around the joint. The fibrosis should provide for long term stability. However, the extra capsular suture technique regularly results in failure. Arthrosis of the joint, at a year or so, is the rule rather exception.
In surgical techniques, the tibia is cut and a segment of it is repositioned to change the geometry in order to stabilize the stifle. Various techniques have been used including: tibial plateau leveling osteotomy (TPLO; Slocum B, Slocum TD; Tibial Plateau Leveling Osteotomy For Repair Of Cranial Cruciate Ligament Rupture In The Canine, Vet. Clin. North Am. 23: 777-795, 1993), cranial closing wedge osteotomy (CWO; Slocum B, Devine T; Cranial Tibial Wedge Osteotomy: A Technique For Eliminating Cranial Tibial Thrust In Cranial Cruciate Ligament Repair, J. Am. Vet. Med. Assoc. 184: 564-569, 1984), and tibial tuberosity advancement (TTA; Tepic S, Damur D M, Montavon P M; Biomechanics Of The Stifle Joint, in Proceedings of the 1st World Orthopaedic Vet. Congress, Munich, Germany, September 2002, pp 189-190). These are significantly invasive procedures which change the overall geometry of the stifle. Of the surgical approaches used in dogs, TTA seems to be associated with lesser morbidity and faster recovery, while providing immediate and durable stability to the joint. Nevertheless, complications and progressing arthrosis are common with each of these techniques.
Intra-articular prostheses are also occasionally used. Again, they require significantly invasive procedures to insert them within the stifle. Even then, they generally end up in failure.